The present invention relates to a magnetic disk apparatus that performs recording and playback by means of a head on a magnetic disk capable of recording and playing back information, and more particularly relates to a format of data tracks on the magnetic disk. This invention further relates to a magnetic information disk provided with data track format information, and a magnetic disk apparatus comprising a magnetic disk to which the format information is transferred and recorded by using the master information desk.
As personal computers have advanced and come into widespread use in recent years, magnetic disk apparatus such as hard disk drives have come to be widely used as external storage devices because of their large capacity and high speed. Along with the increasing size of computer software and the quantities of data handled, ever larger capacities are also demanded of these magnetic disk apparatuses in their role as external storage devices. Moreover, disk drives offering high speed and large capacity are used not only for computers, but also in digital AV products, etc., that record and play back video and voice data using digital technology, and there is a demand for large-capacity magnetic disks for recording and playing back digital AV information that comprises enormous quantities of data.
Conventional magnetic disk apparatuses will be described below.
FIG. 8 is a schematic diagram showing an example of a conventional magnetic disk apparatus. In FIG. 8, the magnetic disk 1 is the medium on which data is recorded: the magnetic head 2 is means for performing recording and playback of information to and from the magnetic disk 1; the actuator 3 has the magnetic head 2 mounted at its tip, and is means for performing positioning operations to an arbitrary radial position on the magnetic disk 1; the head amplifier 5 is means for detecting and amplifying playback signals from the magnetic head 2; the controller 4 is means for detecting the relative position of the magnetic head 2 with respect to the magnetic disk 1 from the output of the head amplifier 5, and outputting a control signal to position the actuator 3 at the prescribed position on the magnetic disk 1; and the driver 6 is means for supplying a current corresponding to the control signal to the actuator 3.
Further, the actuator 3 is composed of a carriage 3a, suspension 3b, drive coil 3c, and permanent magnet 3d or the like.
The carriage 3a is means for causing oscillating motion with point c as the center of rotation. The suspension 3b is attached to the carriage 3a, and is means for causing the magnetic head 2 to float at a constant distance of several tens of nanometers above the surface of the magnetic disk 1 by means of a floatation mechanism called a slider. The drive coil 3c is means for generating a driving force by means of the permanent magnet 3d provided opposite to it, and as a result rotating the actuator 3. The permanent magnet 3d is means for generating a driving force together with the drive coil 3c and rotating the actuator 3.
Also provided, although not illustrated, are a spindle motor for rotational drive of the magnetic disk 1, an interface section that performs exchange of digital information with the host, a buffer that stores this information for efficient recording and playback to and from the magnetic disk 1, together with a buffer control unit, an information recording and playback circuit, etc.
The operation of a conventional disk apparatus will be described below. When the magnetic disk 1 performs information recording and playback, it is rotated at a given speed (5,400 rpm in this conventional example) by the spindle motor (not illustrated). At this time, the magnetic head 2 is positioned above the magnetic disk 1 by means of the actuator 3, and is maintained in a floating state in the position at which the pressure of the suspension 3b provided at the tip of the actuator 3, and the active force of the airflow between the slider formed integrally with the magnetic head 2 (not illustrated) and the magnetic disk 1 are in balance. Position information (b in the drawing) is recorded in advance on each of the tracks forming concentric circles (one track is shown by a dashed line at a in the drawing) on the magnetic disk 1. The position information b is recorded at fixed intervals on each track, and the magnetic head 2 plays back the position information at fixed time intervals in accordance with the rotation of the magnetic disk 1 (this time interval is called the sampling period, and the reciprocal of the sampling period is called the sampling frequency, which is 5.4 kHz in this conventional example). The area in which this position information b is recorded is called a servo area. Information is recorded in or played back from areas other than these servo areas; these areas are called data areas. The playback signal output from the magnetic head 2 is detected and amplified by the head amplifier 5, and input to the controller 4. In the controller 4, position information is detected from the input signal, the positional error relative to the target track a of the magnetic head 2 at that time is computed, the control amount necessary to drive the actuator 3 in order to reduce this positional error is computed, and a control signal is output. In this case, a control method such as phase compensation, for example, is used. The driver 6 supplies the necessary current to the drive coil 3c of the actuator 3 on the basis of the input control signal. By this means, a driving force is generated by the drive coil 3c and the permanent magnet 3d located opposite, and the actuator rotates about point c and constantly positions the magnetic head 2 above the target track a. In this state, information recording and playback is performed on the data area by the magnetic head 2. When information recording and playback is performed in this way, a closed loop positioning control system that positions the magnetic head 2 above the target track is used.
FIG. 9 shows details of the position information formed in the servo area 7a. In this servo area 7a, track identification information, burst patterns, etc., are recorded as servo information for positioning the head 14 which has a write head 15 and a read head 16. The track identification information is information that denotes the track numbers of each data area; it is read by the magnetic head 2, and makes it possible to determine the track position at which the magnetic head 2 is currently positioned. The burst patterns are a plurality (4 in this conventional example) of patterns with mutually differing phases. On the basis of the signals output from these patterns, the amount of drift of the head 2 is detected, and this is used by the controller 4 to constantly follow the prescribed track and position the magnetic head 2 at that track by controlling the actuator 3. To be specific, AGC 9 is an area for fixing the amplitude of the playback waveform by means of an AGC circuit, Sync 10 is an area for achieving clock synchronization, SAM (Servo Address Mark) 11 is an area that denotes the start position of the servo area, Track No. and Wedge No. 12 are the track number and wedge number called the Gray code, and Burst 13 comprises a burst area for generating intra-track position signals.
Therefore, Track No. and Wedge No. 12 constitute track identification information, and Burst 13 corresponds to the burst patterns. When the head detects the SAM (Servo Address Mark) 11, the Track No. and Wedge No. 12 are detected based on that point in time, and the track number and wedge number are identified, and then the burst signal is detected in Burst 13 at the prescribed point in time from that reference point in time, and head positioning is performed by means of the closed loop control system on the basis of that signal.
FIG. 10 shows an example of a 2-phase servo that generates an intra-track position signal, and generates a reference signal for positioning the head 14 on the basis of that position signal. This example will be explained below.
In track 7, servo areas 7a and data areas 7b follow alternately. The case in which track n+1 of a servo area 7a is recorded and played back by the head 14 will be described below.
After the head 14 has passed AGC 9, Sync 10, SAM 11, and Track No. and Wedge No. 12 of track n+1, burst signals are detected four times within a fixed time interval in Burst 13 for generation of the intra-track position signal. 17 is the first burst signal detected, and the vertical axis is the position in the radial direction from the center of rotation. The xe2x80x9c greater than xe2x80x9d shape is the amplitude of the detected signal. Similarly, 18, 19, and 20 denote the detected amplitude of burst signals at the position of the head 14. There are thus four burst signals: A, B, C, and D. 21 comprises the difference between the signal detected at 17 and the signal detected at 18, and is called the N phase. Similarly, 22 is the difference between the amplitude of the signal detected at 19 and the amplitude of the signal detected at 20, and is called the Q phase. The difference in burst signal amplitudes is calculated by means of this pair, N phase 21 and Q phase 22, and the parts of each with high linearity are connected to give a linear phase error signal which is used as the closed loop position control system signal.
In order to perform this kind of preformatting in which servo information is written to a magnetic disk, it is necessary to sequentially position the magnetic head and write the servo information (AGC, Sync, SAM, Track No. and Wedge No., burst patterns, etc.) with a servo track writer. This necessitates highly accurate positioning technology, and at the present time this work requires from several tens of minutes to several hours.
However, the following kinds of problems will arise with the above system.
With the conventional concentric-circle track format, when recording or playing back a large amount of data that is transferred sequentially in time, such as video and voice data, for example, since the data is recorded over a number of tracks, track jump operations (seeks) from one track to the adjacent track are necessary during recording or playback. Conventionally, this takes 20% to 30% of the time required for one disk revolution. Since no recording or playback whatsoever is performed during this time, of course, efficiency becomes extremely poor, and transfer performance falls, when recording or playing back a large amount of data transferred continuously in time. Moreover, when a track jump is normally performed, the next recording or playback can be started within the above-mentioned time, but there are also frequent cases where the operation to stabilize residual oscillation after a track jump (settling) is prolonged, and the next recording or playback position is passed, so that there is a further wait of one revolution. It goes without saying that transfer performance falls further in this case. Maintaining continuous transfer performance during playback of video and voice data is extremely important, and in the above situation, the serious problem of partial halting of video and voice data (frame lapses) will arise.
Also, when a magnetic disk is preformatted, writing to the servo areas by means of a servo track writer requires extremely accurate positioning technology and a large amount of time, and is an obstacle to the mass production of magnetic disks at a low price.
The present invention takes into account the problem of reduced data transfer efficiency and partial loss of data when data transferred continuously in time is recorded or played back, and the problem of the time and cost involved in preformatting magnetic disks, and it is an objective of the present invention to provide a magnetic disk apparatus and master information disk that enable data that is transferred continuously in time to be recorded and played back efficiently, and make it possible for magnetic disk preformatting to be performed in a short time and without cost.
In order to solve the above-mentioned problems, one aspect of the invention is a magnetic disk apparatus comprising:
a head that performs data recording and playback while moving relative to a magnetic disk rotating at the prescribed speed;
an actuator that positions said head relative to said magnetic disk; and
a controller that detects the position of said head by means of servo sector that have positioning information recorded magnetically on said magnetic disk and performs control to position said actuator by means of this detection signal, wherein said magnetic disk has at least a part in which the arrangement of tracks having at least said servo sectors is spiral, and a ferromagnetic film or ferromagnetic powder coating phase is formed on the surface of said magnetic disk, and with regard to the master information disk, depressions and projections corresponding to said positioning information are formed on the surface of the disk substrate, and at least the raised surfaces of said depressions and projections are a ferromagnetic medium, and said depressions and projections are formed in a spiral, and by bringing the surface of the master information disk into contact with the surface of said magnetic disk, a magnetized pattern corresponding to said depressions and projections is recorded.
Another aspect of the invention is a magnetic disk apparatus, wherein said magnetic disk comprises an area in which the tracks are formed spirally, and an area in which the tracks are formed in concentric circles.
Still another aspect of the invention is a magnetic disk apparatus, wherein the area in which said tracks are formed in concentric circles is formed on the side nearer the center of rotation of said magnetic disk, and the area in which said tracks are formed spirally is formed on the side further from said center of rotation.
Yet another aspect of the invention is a magnetic disk apparatus wherein the area in which said tracks are formed spirally and the area in which said tracks are formed in concentric circles are arranged with the provision of intervals to prevent said servo sector positioning information of at least said mutually adjacent areas from overlapping.
Still yet another aspect of the invention is a master information disk comprising a disk substrate on which depressions and projections corresponding to positioning information held by the servo sectors are formed, wherein at least the raised surfaces of said depressions and projections are magnetized, and at least part of said depressions and projections are formed in a spiral on said disk substrate, and which is used to record a magnetized pattern corresponding to said depressions and projections on a magnetic disk by being brought into contact with said magnetic disk.
Next, the operation of the present invention will be described.
The magnetic disk apparatus of the present invention comprises a rotating magnetic disk, a head that records and plays back information while moving relative to the magnetic disk, and an actuator that supports the head and moves and positions the head almost radially on the aforesaid magnetic disk in accordance with commands, with the actuator being a device that positions the head in accordance with position information recorded magnetically in servo sectors on the magnetic disk, and the position information being formed spirally on the magnetic disk. By this means, recording and playback are performed with the head following the spiral track, so that recording and playback of large amounts of continuous data, such as video and voice data, can be performed efficiently without track jumps. In addition, revolution waits due to track jumps are also eliminated, with the result that continuous transfer performance is greatly improved and video frame lapses, etc., no longer occur.
Further, the use of the master information disk of the present invention eliminates the need for high-speed, high-precision positioning technology and the time required for writing associated with writing servo sectors with a servo track writer, and makes it possible to reduce the cost of construction of the magnetic disk apparatus of the present invention.